The present invention relates to the field of encoding arrangements for generating groups of coded binary signals representing the operation of respective individual keys of a keyboard.
Keyboards are used in a variety of systems as the user interface. In such systems, there is usually a decoding arrangement for generating groups of binary signals representing the operation of respective individual keys or push buttons.
One type of encoding arrangement includes a static logic network comprising, for example, a diode matrix in which diodes are coupled between row and column conductors associated with respective rows and columns in which the keys are located. When a key is depressed, appropriate diodes are rendered conductive and nonconductive to generate a respective group of coded binary signals representing the operation of the key. Such encoding arrangements tend to be expensive because at least one diode is associated with each key.
Encoding arrangements are also known which employ keys with multiple contacts, each associated with a respective binary signal of a group of encoded binary signals. When a key is depressed, the contacts associated with the key make contact to generate a respective group of coded binary signals representing operation of the key. While such systems tend to be less expensive than the ones utilizing static logic networks, they tend to be less reliable because of their mechanical nature.
Still other encoding arrangements are of a scanning type which, for example, sequentially couple signals to respective row (or column) conductors associated with respective rows (or columns) in which the keys of a keyboard are located. When a key is depressed, one of the sequentially generated signals is coupled through its closed contacts and an associated column (or row) of conductors to an encoding logic network. The encoding logic network generates a group of coded binary signals representing the depressed key in accordance with the time relationship of the received one of the sequentially generated signal. While such types of encoding arrangements tend to be less expensive than the static logic types of encoding arrangements and more reliable than the mechanical types of encoding arrangements, they are intended to be separate parts of a system with which they are employed and are therefore not well suited to being incorporated as an integral part of the system. As a result, such encoding arrangements tend to require extra connections and input terminals for integrated circuits which may be utilized in the system for which the keyboard is the interface.